1. Field of the Invention
This invention relates to an oblique-shaft axial piston machine having piston elements articulated in a drive disc fixedly connected to a drive shaft. The transmission of torque between the drive shaft, (which may be in the form of a drive disc), and a rotatably mounted cylinder drum supported on a rider and having axial cylinder bores in which the piston elements travel to and fro, is effected exclusively by piston rod portions of the piston elements. The piston elements, in at least one definite rotational position of the drive disc and cylinder drum, meet the edges of slot-like openings in a following plate connected to the cylinder drum. The width of these slot-like openings is somewhat less than the diameter of the cylinder bores.
2. Description of the Prior Art
In modern, compact axial piston machines of light-weight construction and incorporating oblique-shaft design, generally the cylinder drum is carried along directly by the piston rods, or by follower portions of piston elements, if the piston and piston rod take the form of a one-piece piston element.
In a known version of such a machine using direct propulsion of the cylinder drum, the piston rods, or follower areas of the piston elements, bear directly on the inside wall of the cylinder bores and thus transmit the requisite torque for turning the cylinder drum. A disadvantage of this approach is that the bearing takes place at the sealing surface of the cylinder bores. Since the propulsion by contact of the piston rods with the cylinder bores takes place only at definite rotational positions, and owing to the kinematic non-uniformity of the piston motion, concussions occur between the piston rod or piston element and the cylinder bore. In prolonged service of the machine, this may cause damage to the surface of the cylinder bore and hence impairment of the seal of the piston in the cylinder bore. In this connection, reference is made to German Public Disclosure Nos. DE-AS 2,262,026 and DE-AS 2,358,870.
In an oblique-shaft axial piston machine of the type referred to above and shown and described in U.S. Pat. No. 1,137,283, (corresponding to German Pat. No. 249,477), this hazard is avoided in that the cylinder drum is carried along by way of a separate follower plate, fixedly connected, however, to the cylinder. The follower plate is arranged on the side of the cylinder drum towards the drive disc. The follower plate takes the form of a star-shaped part having slot-like openings opening outward. The clear apertures of the openings are somewhat less than the diameter of the cylinder bores, but greater than that of the tapered piston rods, so that in a definite rotational position, the piston rods will meet an inner edge of the openings and propel the cylinder drum.
One-piece piston elements, as well as composite piston elements composed of a piston part and a piston rod, in modern axial piston machines, cannot be disassembled. This means that for installation of the follower plate, its openings must be radially accessible so that the piston elements or piston rods can be inserted. These radially accessible openings greatly weaken the follower plate, unless it is made so thick as to constitute an undesirably great additional weight, which must revolve together with the cylinder drum in operation of the machine. Given the long piston and piston rod service life attainable nowadays, the follower plate with radially accessible openings presents problems of strength.
It is an object of this invention to provide an improved follower plate of the type referred to above which is of light weight construction and which is capable of long service life in spite of the dynamic impact loads described above.
To achieve this object, in an oblique-shaft axial piston machine of the kind described above, it is proposed that the follower plate be fixedly connectable to a locking part that completes each opening to form a hole enclosed all around, so that the follower plate, together with the locking part, forms a stable follower disc. In one embodiment, the locking plate extends in the same plane as the follower plate and is of the same thickness. Thus, a stable follower disc results, which can be made comparatively thin, since the locking part, by closing the radially extending openings of the follower plate, stiffens the latter. Hence, the plate is substantially better able to transmit torque then the prior art star-shaped follower plate with radially extending openings.
In another embodiment of the invention, the locking part is in radially fixed, toothed engagement with the follower plate.
With the follower plate in the form of a more or less star-shaped part with openings opening radially outward, in a further embodiment, the locking part is an outer ring encircling the follower plate. Then the toothed engagement may be provided either by projections extending radially inward from the outer ring into recesses on the periphery of the follower plate, or by projections extending radially inward from the outer ring and fitting into the slot-like openings of the follower plate radially from without. Thus, mutual support of the flanks of the openings is provided, leading to an especially favorable design for transmission of torque by the follower disc.
With the follower plate in the form of an annular part with openings opening radially inward, the locking part, in another embodiment of the invention, takes the form of an inner ring. In this case toothed engagement is provided by projections extending radially outward from the inner ring and fitting into the openings of the follower plate radially from within. This too provides a follower plate of light-weight constructon for transmission of high torque.